linux-kernel - Re: [PATCH 5/5] sched/fair: narrow the sched_use_asym

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Date: Tue, 23 Jan 2024 14:17:00 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: alexs@...nel.org
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira
 <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] sched/fair: narrow the sched_use_asym_prio checking
 scenario



On 1/17/24 2:27 PM, alexs@...nel.org wrote:
> From: Alex Shi <alexs@...nel.org>
> 
> Current function doesn't match it's comments, in fact, core_idle
> checking is only meaningful with non-SMT.
> So make the function right.
> 
> Signed-off-by: Alex Shi <alexs@...nel.org>
> To: Valentin Schneider <vschneid@...hat.com>
> To: Vincent Guittot <vincent.guittot@...aro.org>
> To: Peter Zijlstra <peterz@...radead.org>
> To: Ingo Molnar <mingo@...hat.com>
> ---
>  kernel/sched/fair.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 96163ab69ae0..0a321f639c79 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9741,8 +9741,8 @@ group_type group_classify(unsigned int imbalance_pct,
>   */
>  static bool sched_use_asym_prio(struct sched_domain *sd, int cpu)
>  {
> -	return (!sched_smt_active()) ||
> -		(sd->flags & SD_SHARE_CPUCAPACITY) || is_core_idle(cpu);
> +	return	(sd->flags & SD_SHARE_CPUCAPACITY) ||
> +		(!sched_smt_active() && is_core_idle(cpu));
>  }

This seems wrong. This would always return false for higher than SMT domains 
if smt is active. 

Was this meant to be sched_smt_active() && is_core_idle(cpu)? 

>  
>  static inline bool _sched_asym(struct sched_domain *sd,